JP5046621B2 - Refrigeration system and method of operating refrigeration system - Google Patents

Description

  The present invention relates to a refrigeration system and an operation method thereof, and more particularly, to a refrigeration system including an air refrigerant refrigerator and an operation method thereof.

  One method of cryopreservation of food is to first create ice capsules on the surface of the food at ultra-low temperatures, then increase the freezing temperature to balance the temperature of the surface and center of the food, and then again by rapid freezing. A method is known in which the whole food is frozen and then transferred to a cryopreservation temperature.

  Patent Document 1 discloses a food freezing apparatus capable of performing the above-described cryopreservation method. The freezing apparatus includes a freezing chamber that surrounds a conveyor that conveys food to be frozen. A first refrigeration stage using a liquefied gas, a second refrigeration stage using a refrigeration cycle, a third refrigeration stage using a liquefied gas, and a fourth refrigeration stage using a refrigeration cycle are provided in the freezer compartment from the inlet side toward the outlet side. . In the first and third stages, an atmosphere of −50 ° C. to −90 ° C. is created by spraying the liquefied gas. In the second and fourth stages, an atmosphere of −20 ° C. to −45 ° C. is created by the refrigeration cycle. In the second and fourth stages, refrigeration cycle evaporators are provided on both sides of the conveyor. In these evaporators, heat exchange is performed between the refrigerant and the atmosphere.

  Patent Document 1 describes the temperature of the atmosphere in each stage as follows. If the temperature of the atmosphere in the first stage is higher than −50 ° C., quick freezing necessary for making ice capsules on the surface of the food cannot be performed, and if it is lower than −90 ° C., cracks are likely to occur on the surface of the food. And protein denaturation tends to occur. If the temperature of the atmosphere in the second stage is higher than −20 ° C., the next quick freezing will be hindered. May occur. If the temperature of the atmosphere in the third stage is higher than −50 ° C., it takes time to pass through the maximum ice crystal generation temperature zone, so fine ice crystals cannot be obtained, and if it is lower than −90 ° C., the surface of the food is cracked. And protein denaturation is likely to occur. In the fourth stage, the food frozen in the previous stage is deep frozen. At this time, since the food is already at a temperature below the maximum ice crystal formation temperature zone, relatively slow cooling is sufficient. Still, if the temperature of the atmosphere is higher than −20 ° C., this deep freezing takes too much time, and if it is lower than −45 ° C., the food may crack.

  On the other hand, Patent Document 2 discloses an air refrigerant refrigerator. This air refrigerant refrigerator can efficiently cool the air in the freezer compartment. However, since the air in the freezer compartment circulates through the compressor, heat exchanger, and expansion turbine provided in the air refrigerant refrigerator, it is necessary to frequently defrost when the air contains a large amount of moisture.

Japanese Utility Model Publication No. 5-53491 JP 2002-310523 A

  An object of the present invention is to provide a refrigeration system that prevents moisture from being brought into the air refrigerant refrigerator and an operation method thereof.

  Hereinafter, means for solving the problem will be described using the numbers used in (Best Mode for Carrying Out the Invention). These numbers are added to clarify the correspondence between the description of (Claims) and (Best Mode for Carrying Out the Invention). However, these numbers should not be used to interpret the technical scope of the invention described in (Claims).

  The refrigeration system according to the present invention includes a freezing room (2) partitioned into a precooling room (2a) and a main freezing room (2b), and a freezing object (11) in which the precooling room and the main freezing room are arranged in this order. A conveyor (4) that conveys the object to be frozen so as to pass through, a liquid nitrogen supply device (5) that supplies liquid nitrogen into the precooling chamber, and an air refrigerant refrigerator (12). The air refrigerant refrigerator takes air from the main freezer compartment, compresses the taken air, cools the compressed air, expands the cooled air by an expansion turbine, and expands the expanded air into the main freezer compartment. It is configured to return.

  When an air refrigerant refrigerator is applied to a conveyor-type refrigeration apparatus in which outside air is likely to flow in, moisture is brought into the air refrigerant refrigerator. According to the present invention, by freezing the surface portion of the object to be frozen in the pre-cooling chamber, moisture from the object to be frozen is prevented from being brought into the air refrigerant refrigerator.

  In the refrigeration system of the present invention, it is preferable that the liquid nitrogen supply device is configured to eject liquid nitrogen into the precooling chamber.

  The refrigeration system according to the present invention includes an exhaust cold air recovery duct (13) connecting the air refrigerant refrigerator and the main freezer compartment, and a cold air supply duct (25) connecting the air refrigerant refrigerator and the main freezer chamber. It is preferable to comprise. The conveyor carries the object to be frozen into the main freezer compartment from a connection port (2d) connecting the precooling chamber and the main freezer compartment, and carries it out from an outlet (2e) provided in the main freezer compartment. It is preferable to be provided. It is preferable that the exhaust cool air recovery port (13a) of the exhaust cool air recovery duct is disposed on the outlet side in the main freezer compartment. It is preferable that the cold air supply port (25a) of the cold air supply duct is disposed on the connection port side in the main freezer compartment. The air refrigerant refrigerator takes in the air in the main freezer compartment from the exhaust cold air recovery port, compresses the taken-in air, cools the compressed air, and expands the cooled air by the expansion turbine. It is preferable that air is returned from the cold air supply port to the main freezer compartment.

  The refrigeration system according to the present invention preferably comprises a seat (7). The conveyor is provided to carry the object to be frozen into the main freezer compartment through a connection port (2d) connecting the precooling chamber and the main freezer compartment, and to carry out the object from an outlet provided in the main freezer compartment. It is preferable. It is preferable that the sheet is provided so as to be able to partially block the connection port.

  The refrigeration system according to the present invention preferably includes a winding device (8) for winding the sheet.

  The refrigeration system according to the present invention preferably includes a temperature sensor (10) for detecting the temperature in the main freezer compartment and a control device (30). The control device may start ejecting liquid nitrogen to the liquid nitrogen supply device and start the operation of the air refrigerant refrigerator when the winding device is in a state of winding the sheet. preferable. It is preferable that the control device causes the winding device to rewind the sheet based on the fact that the temperature has decreased below a predetermined temperature.

  The refrigeration system according to the present invention includes a temperature sensor (9) for detecting the temperature in the precooling chamber, and an amount of liquid nitrogen ejected by the liquid nitrogen supply device so that the temperature is lower than -90 ° C and higher than -196 ° C. It is preferable to comprise the control apparatus (3) to control.

  In the operation method of the refrigeration system according to the present invention, the refrigeration system includes a freezing chamber (2) partitioned into a precooling chamber (2a) and a main freezing chamber (2b), and a freezing object (11) is the precooling chamber. And a conveyor (4) for transporting the object to be frozen so as to pass through the main freezer compartment in this order, and an air refrigerant refrigerator (12). The air refrigerant refrigerator takes air from the main freezer compartment, compresses the taken air, cools the compressed air, expands the cooled air by an expansion turbine, and expands the expanded air into the main freezer compartment. It is configured to return. The operating method of the refrigeration system includes a step of operating the air refrigerant refrigerator while supplying liquid nitrogen into the precooling chamber.

  In the operation method of the refrigeration system according to the present invention, in the step of operating the air refrigerant refrigerator, it is preferable to operate the air refrigerant refrigerator while spouting liquid nitrogen into the precooling chamber.

  In the operation method of the refrigeration system according to the present invention, the refrigeration system preferably includes a seat (7). The conveyor carries the object to be frozen into the main freezer room through a connection port (2d) connecting the precooling room and the main freezer room, and carries out the object from an outlet (2e) provided in the main freezer room. Is preferably provided. It is preferable that the sheet is provided so as to be able to partially block the connection port. The operation method of the refrigeration system starts to eject liquid nitrogen into the precooling chamber when the seat is in a state of blocking a relatively small portion of the connection port, and the operation of the air refrigerant refrigerator And a step of closing a relatively large portion of the connection port with the sheet based on the fact that the temperature in the main freezer compartment has dropped below a predetermined temperature.

  In the start step of the operation method of the refrigeration system according to the present invention, it is preferable that the operation of the air refrigerant refrigerator is started after the start of jetting of liquid nitrogen into the precooling chamber.

  In the operation method of the refrigeration system according to the present invention, the conveyor carries the object to be frozen into the main freezer compartment through a connection port (2d) connecting the precooling chamber and the main freezer compartment, and enters the main freezer compartment. It is preferable to be provided so as to be carried out from the provided outlet (2e). In the step of operating the air refrigerant refrigerator, the air refrigerant refrigerator takes air from the outlet side in the main freezer compartment, compresses the taken air, cools the compressed air, It is preferable that the air expanded by the expansion turbine is returned to the connection port side in the main freezer compartment.

  In the step of operating the air refrigerant refrigerator of the operation method of the refrigeration system according to the present invention, the amount of liquid nitrogen sprayed into the precooling chamber is such that the temperature in the precooling chamber is lower than -90 ° C and higher than -196 ° C. Preferably it is controlled.

  ADVANTAGE OF THE INVENTION According to this invention, the refrigerating system which prevents that moisture is carried in into an air refrigerant refrigerator, and its operating method are provided.

  The best mode for carrying out the refrigeration system and the operation method of the refrigeration system according to the present invention will be described below with reference to the accompanying drawings.

(Configuration of refrigeration system)
FIG. 1 shows an overall view of a refrigeration system 1 according to an embodiment of the present invention. The refrigeration system 1 freezes only the surface portion of the object 11 to be frozen using liquid nitrogen in the pre-cooling chamber 2a, and then freezes to the central portion using the air refrigerant refrigerator 12 in the main freezing chamber 2b. The refrigeration system 1 includes a freezer compartment 2, a conveyor 4, a liquid nitrogen supply device 5, a sheet 7, a winding device 8, a temperature sensor 9, a temperature sensor 10, an air refrigerant refrigerator 12, an exhaust cool air The recovery duct 13, the cold air supply duct 25, and a control device 30 described later are provided. The freezer compartment 2 is partitioned into a precooling compartment 2a and a main freezer compartment 2b. The precooling chamber 2a is provided with an inlet 2c. A connection port 2d for connecting the precooling chamber 2a and the main freezing chamber 2b is provided. The main freezer compartment 2b is provided with an outlet 2e. In the conveyor 4 (example: belt conveyor), the object 11 to be frozen enters the precooling chamber 2a from the inlet 2c, passes through the precooling chamber 2a, enters the main freezing chamber 2b through the connection port 2d, and passes through the main freezing chamber 2b. The frozen object 11 is conveyed so as to exit from the outlet 2e. The liquid nitrogen supply device 5 ejects liquid nitrogen into the precooling chamber 2a. The temperature sensor 9 detects the temperature in the precooling chamber 2a. The exhaust cool air recovery duct 13 connects the main freezer compartment 2 b and the air refrigerant refrigerator 12. The cold air supply duct 25 connects the main freezer compartment 2 b and the air refrigerant refrigerator 12. The air refrigerant refrigerator 12 takes in the air in the main freezer compartment 2 b from the exhaust cold air collection port 13 a of the exhaust cold air recovery duct 13, cools the taken air, and cools the cooled air from the cold air supply port 25 a of the cold air supply duct 25. Return to main freezer 2b. The temperature sensor 10 detects the temperature in the main freezer compartment 2b. The sheet 7 is provided so as to be able to partially block the connection port 2d. Here, partially closing the connection port 2d means closing the conveyor 4 so that the object 11 to be frozen can be conveyed. As shown in FIG. 2, the winding device 8 rotates the roller on which the sheet 7 is attached in the forward and reverse directions to wind up and rewind the sheet 7. The wound sheet 7 closes a relatively small portion of the connection port 2d. The sheet 7 in the rewound state closes a relatively large portion of the connection port 2d. By winding and unwinding the sheet 7, the movement of gas between the pre-cooling chamber 2a and the main freezing chamber 2b and the accompanying heat transfer are adjusted.

  FIG. 3 shows a system diagram of the air refrigerant refrigerator 12. In FIG. 3, all pressures are shown as absolute pressures. The air refrigerant refrigerator 12 includes a main freezer compartment outlet side valve 14, a first pipe 15, a compressor 16, a motor 17, an expansion turbine 18, a cooling radiator 20, a cooling fan 21, and a second pipe 22. And a third pipe 23, a main freezer compartment inlet side valve 24, a first heat exchanger 26, an exhaust heat recovery heat exchanger 27, a defroster 28, and a defrost line 29. The compressor 16, the motor 17, and the expansion turbine 18 form a uniaxial turbine unit 19. The compressor 16 and the expansion turbine 18 are driven by a motor 17. The compressor 16 is provided on one side of the rotor of the motor 17, and the expansion turbine 18 is provided on the other side of the rotor. The motor 17 is oil-free by supporting the rotor with a magnetic bearing 17a. The motor 17 is cooled by the cooling radiator 20 and the cooling fan 21. The main freezer compartment outlet side valve 14 is a three-way valve having three ports 14a to 14c. The main freezer compartment inlet side valve 24 is a two-way valve provided with two ports 24a and 24b. In the exhaust air collecting duct 13, the opposite side of the exhaust air collecting port 13a is connected to the port 14a. The first pipe 15 connects the port 14 b and the inlet of the compressor 16. The second pipe 22 connects the outlet of the compressor 16 and the inlet of the expansion turbine 18. The third pipe 23 connects the outlet of the expansion turbine 18 and the port 24a. The cold air supply duct 25 has the opposite side of the cold air supply port 25a connected to the port 24b. The first heat exchanger 26 is provided in the second pipe 22. The exhaust heat recovery heat exchanger 27 is provided across the portion of the second pipe 22 on the downstream side of the first heat exchanger 26 and the first pipe 15. That is, the first heat exchanger 26 is disposed on the compressor 16 side (upstream side) of the second pipe 22, and the exhaust heat recovery heat exchanger 27 is disposed on the expansion turbine 18 side (downstream side) of the second pipe 22. Yes. The defroster 28 is provided in the third pipe 23. The defrost line 29 connects the port 14c and a portion of the third pipe 23 between the defroster 28 and the main freezer compartment inlet-side valve 24. The defrost line 29 is used when the air refrigerant refrigerator 12 is defrosted.

  In the refrigeration system 1, the air in the main freezer compartment 2b is directly cooled by the refrigeration cycle of the air refrigerant refrigerator 12, so that the air in the main freezer compartment 2b is cooled by the refrigeration cycle using the chlorofluorocarbon refrigerant. It is not necessary to provide a heat exchanger (evaporator) in the main freezer compartment 2b. Therefore, the main freezer compartment 2b can be easily downsized.

  Moreover, if a filter is provided in the exhaust cool air collecting duct 13, the maintainability of the refrigeration system 1 is improved.

  FIG. 4 shows a control system of the refrigeration system 1. The temperature sensor 9 detects the temperature in the precooling chamber 2 a and inputs it to the control device 30. The temperature sensor 10 detects the temperature in the main freezer compartment 2 b and inputs it to the control device 30. The control device 30 controls each of the conveyor 4, the liquid nitrogen supply device 5, the winding device 8, and the air refrigerant refrigerator 12.

(Operation method of refrigeration system)
First, the operation method of the refrigeration system 1 during the refrigeration operation will be described. The sheet 7 is in a state of being rewound by the winding device 8 and closes a relatively large portion of the connection port 2d. The object 11 to be frozen is conveyed by the conveyor 4 and enters the freezer compartment 2 from the inlet 2c, passes through the precooling chamber 2a, the connection port 2d, and the main freezer compartment 2b in this order, and exits from the freezer compartment 2 through the outlet 2e. At this time, the surface of the object 11 to be frozen is frozen by liquid nitrogen in the precooling chamber 2a. Then, the object 11 to be frozen is frozen to the central portion in the main freezer compartment 2b. Since the frozen object 11 is carried into the main freezer compartment 2b with the surface portion frozen, the moisture of the frozen object 11 is prevented from moving into the atmosphere and being brought into the air refrigerant refrigerator 12. By the freezing operation, the frozen object 11 having an initial temperature of 20 ° C. is frozen to −60 ° C.

  As shown in FIG. 3, the temperature of the air taken into the air refrigerant refrigerator 12 from the main freezer compartment 2b through the exhaust air collecting duct 13 is −60 ° C., and the pressure (absolute pressure, the same applies hereinafter) is 0. .1 MPa. While this air flows into the compressor 16 via the first pipe 15, heat is exchanged with the air flowing through the second pipe 22 in the exhaust heat recovery heat exchanger 27, and the temperature is 29 ° C. and the pressure is 0. .1 MPa. Thereafter, this air is adiabatically compressed in the compressor 16 to a temperature of 114 ° C. and a pressure of 0.2 MPa. Thereafter, the air is exchanged with the heat medium (for example, water) in the first heat exchanger 26 while flowing into the expansion turbine 18 via the second pipe 22, and then the exhaust heat recovery heat exchange. Heat is exchanged between the air flowing through the first pipe 15 in the vessel 27. The air is cooled when passing through the first heat exchanger 26, and the temperature and pressure become 37 ° C. and 0.2 MPa. The air is cooled when passing through the exhaust heat recovery heat exchanger 27, and the temperature and pressure become -52 ° C and 0.2 MPa. Thereafter, the air is adiabatically expanded in the expansion turbine 18, frost is removed in the defroster 28, and then returned to the main freezer compartment 2 b via the cold air supply duct 25. The air at this time has a temperature of −85 ° C. and a pressure of 0.1 MPa.

  As described above, the object 11 to be frozen is carried into the main freezer compartment 2b with the surface portion frozen. Therefore, moisture of the object 11 to be frozen is prevented from moving into the atmosphere and being brought into the air refrigerant refrigerator 12 together with the atmosphere. Therefore, it is not necessary to frequently defrost the air refrigerant refrigerator 12. Further, when moisture forms ice blocks, the blades of the expansion turbine 18 may be damaged by the ice blocks. Since the air refrigerant refrigerator 12 cannot be used for a long period of time during the replacement of the turbine blades, it is important to prevent moisture from being brought into the air refrigerant refrigerator 12. The air refrigerant refrigerator 12 can supply cold air having a very low temperature of −85 ° C. into the main freezer compartment 2b. In order to prevent the formation of frost or ice blocks in the air refrigerant refrigerator 12, it is necessary to make the temperature of the surface portion of the object 11 to be frozen very low. Therefore, the control device 30 determines the amount of liquid nitrogen that the liquid nitrogen supply device 5 ejects into the precooling chamber 2a so that the temperature in the precooling chamber 2a detected by the temperature sensor 9 is lower than -90 ° C and higher than -196 ° C. It is preferable to control. In addition, liquid nitrogen may be applied to the frozen object 11 in a liquid state, or may be sprayed on the frozen object 11 in a gas state.

  In addition, the control device 30 causes the liquid nitrogen so that the nitrogen gas obtained by vaporizing the liquid nitrogen ejected into the precooling chamber 2a flows into the main freezing chamber 2b from the connection port 2d and increases the pressure in the main freezing chamber 2b. It is preferable to control the amount of liquid nitrogen ejected by the supply device 5. In this case, air containing moisture is prevented from flowing into the main freezer compartment 2b from the outlet 2e.

  Here, since low-temperature nitrogen gas flows from the connection port 2d, the temperature on the connection port 2d side in the main freezer compartment 2b is lowered. Therefore, it is preferable that the exhaust cool air recovery port 13a is disposed on the outlet 2e side in the main freezer compartment 2b, and the cool air supply port 25a is disposed on the connection port 2d side in the main freezer compartment 2b. The air in the main freezer compartment 2b is efficiently cooled by the air refrigerant refrigerator 12 taking in air from the outlet 2e side having a relatively high temperature.

  It is also possible to dispose the cool air collection port 13a on the connection port 2d side and the cool air supply port 25a on the exit 2e side. In this case, the air flowing in the main freezer compartment 2b from the cold air supply port 25a to the exhaust cold air recovery port 13a is opposed to the object 11 to be frozen, so heat exchange between the air and the object 11 to be frozen is performed. Increased efficiency.

According to the thermal calculation result for the case where tuna seeds having an initial temperature of 20 ° C. are frozen by the refrigeration system 1 to −60 ° C., the conveying speed of the conveyor 4 is 1.1 m / s, and the passing time of the precooling chamber 2 a is 1 The passage time of the main freezer compartment 2b was 25 minutes, the output of the liquid nitrogen supply device 5 was 3 kW, and the output of the air refrigerant refrigerator 12 was 30 kW. Here, the size of the tuna is 200 × 80 × 20 mm, the mass is 320 g / piece, the specific heat is 0.41 kcal / (kg · K), the surface heat transfer coefficient is 8 W / (m ² · K), and the processing amount is 400 kg / h (1250 pieces / h) was used. In the refrigeration system 1, the running cost is reduced as compared with the case of freezing using only liquid nitrogen.

  Next, an operation method of the refrigeration system 1 at the time of startup from the stopped state will be described. In the stopped state, the conveyor 4 is stopped. The sheet 7 is wound up by the winding device 8 and closes a relatively small portion of the connection port 2d. The liquid nitrogen supply device 5 does not jet liquid nitrogen into the precooling chamber 2a. The air refrigerant refrigerator 12 is stopped.

  The control device 30 causes the liquid nitrogen supply device 5 to start ejecting liquid nitrogen, and causes the air refrigerant refrigerator 12 to start operation. At this time, the pre-cooling chamber 2a is cooled by liquid nitrogen, and the main freezing chamber 2b is a refrigeration cycle performed by the low-temperature nitrogen gas vaporized from the liquid nitrogen through the connection port 2d and by the air refrigerant refrigerator 12 It is cooled by.

  The control device 30 causes the winding device 8 to rewind the sheet 7 based on the fact that the temperature detected by one or both of the temperature sensors 9 and 10 is lower than a predetermined temperature (example: −90 ° C.). . The sheet 7 closes a relatively large portion of the connection port 2d in the rewound state.

  The control device 30 causes the conveyor 4 to start operation after causing the winding device 8 to rewind the sheet 7. Thereby, the refrigeration system 1 will be in a freezing operation state.

  Here, if the timing at which the liquid nitrogen supply device 5 starts to eject liquid nitrogen and the timing at which the air refrigerant refrigerator 12 starts operation coincide with each other, the entire refrigeration system 1 is cooled in a short time. If the timing of starting the operation of the air refrigerant refrigerator 12 is delayed, the air in the main freezer compartment 2b is expelled by the vaporized nitrogen gas, so that moisture is prevented from being brought into the air refrigerant refrigerator 12 at startup. Can be removed. The control device 30 may cause the air refrigerant refrigerator 12 to start operation after a lapse of a predetermined time after starting to eject liquid nitrogen, and after starting to eject liquid nitrogen, the temperature sensor The air refrigerant refrigerator 12 may be started to operate based on the temperature detected by 10 being lower than a predetermined temperature.

  In addition, a liquid nitrogen tank may be provided in the precooling chamber 2a, and liquid nitrogen may be supplied thereto by the liquid nitrogen supply device 5. In this case, the conveyor 4 conveys the frozen object 11 so that the frozen object 11 passes through the liquid nitrogen tank.

FIG. 1 is an overall view of a refrigeration system according to an embodiment of the present invention. FIG. 2 is a partially enlarged view of the refrigeration system according to the embodiment of the present invention. FIG. 3 is a system diagram of an air refrigerant refrigerator provided in the refrigeration system according to the embodiment of the present invention. FIG. 4 is a block diagram showing a control system of the refrigeration system according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Freezing system 2 ... Freezing room 2a ... Pre-cooling room 2b ... Main freezing room 2c ... Inlet 2d ... Connection port 2e ... Outlet 4 ... Conveyor 5 ... Liquid nitrogen supply device 7 ... Sheet 8 ... Winding device 9, 10 ... Temperature sensor DESCRIPTION OF SYMBOLS 11 ... Freezing object 12 ... Air refrigerant refrigerator 13 ... Exhaust cold wind collection | recovery duct 13a ... Exhaust cold wind collection | recovery port 14 ... Main freezer compartment outlet side valve 14a, 14b, 14c ... Port 15 ... 1st piping 16 ... Compressor 17 ... Motor 17a ... magnetic bearing 18 ... expansion turbine 19 ... turbine unit 20 ... cooling radiator 21 ... cooling fan 22 ... second pipe 23 ... third pipe 24 ... main freezer compartment inlet side valves 24a, 24b ... port 25 ... cold air supply duct 25a ... Cold air supply port 26 ... first heat exchanger 27 ... exhaust heat recovery heat exchanger 28 ... defroster 29 ... defrost line 30 ... control device

Claims (4)

A freezer compartment partitioned into a precooling compartment and a main freezer compartment;
A conveyor that conveys the frozen object so that the frozen object passes through the pre-cooling chamber and the main freezing chamber in this order;
A liquid nitrogen supply device for supplying liquid nitrogen into the precooling chamber;
An air refrigerant refrigerator,
Sheet,
A winding device for winding the sheet;
A temperature sensor for detecting the temperature in the main freezer compartment;
And a control device ,
The air refrigerant refrigerator takes air from the main freezer compartment, compresses the taken air, cools the compressed air, expands the cooled air by an expansion turbine, and expands the expanded air into the main freezer compartment. Configured to return,
The liquid nitrogen supply device is configured to eject liquid nitrogen into the precooling chamber,
The conveyor is provided to carry the object to be frozen into the main freezer compartment from a connection port connecting the precooling chamber and the main freezer compartment, and to carry out the object from an outlet provided in the main freezer compartment,
The sheet is provided so as to be able to partially block the connection port,
The controller is
When the winding device is in the state of winding the sheet, the liquid nitrogen supply device is started to spout liquid nitrogen, and the air refrigerant refrigerator is started to operate,
Rewinding the sheet to the winding device based on the temperature being lower than a predetermined temperature,
A refrigeration system that causes the conveyor to start operation after causing the winding device to rewind the sheet . A method of operating a refrigeration system,
The refrigeration system includes:
A freezer compartment partitioned into a precooling compartment and a main freezer compartment;
A conveyor that conveys the frozen object so that the frozen object passes through the pre-cooling chamber and the main freezing chamber in this order;
An air refrigerant refrigerator,
Sheet and
Comprising
The air refrigerant refrigerator takes air from the main freezer compartment, compresses the taken air, cools the compressed air, expands the cooled air by an expansion turbine, and expands the expanded air into the main freezer compartment. Configured to return,
The conveyor is provided so as to carry the object to be frozen into the main freezing room from a connection port connecting the precooling room and the main freezing room, and to carry out from the outlet provided in the main freezing room,
The sheet is provided so as to be able to partially block the connection port,
The operation method of the refrigeration system is:
Starting the liquid nitrogen into the precooling chamber and starting the operation of the air refrigerant refrigerator when the seat is in a state of closing a relatively small portion of the connection port; and
A step of closing a relatively large portion of the connection port with the sheet based on the fact that the temperature in the main freezer compartment is lower than a predetermined temperature;
Operating the air refrigerant refrigerator while blowing liquid nitrogen into the precooling chamber;
Comprising
After the process of closing a relatively large part of the connection port with the sheet, the conveyor starts operation.
How to operate the refrigeration system . In the start step, the operation of the air refrigerant refrigerator is started after the start of jetting of liquid nitrogen into the precooling chamber.
The operating method of the refrigeration system according to claim 2 . In the step of operating the air refrigerant refrigerator, the amount of liquid nitrogen sprayed into the precooling chamber is controlled so that the temperature in the precooling chamber is lower than −90 ° C. and higher than −196 ° C.
The operating method of the refrigeration system of Claim 2 or 3 .

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